Air Sharing

The emergency procedure in which one diver supplies breathing gas to another, usually via the octopus, followed by a controlled ascent together.

Air sharing is the procedure for supplying breathing gas to a diver who has run out or whose gas has become unbreathable. In recreational diving the standard version uses the donor's octopus, the yellow alternate second stage: the out-of-air diver signals with a hand slashing across the throat, the donor presents the octopus, the receiver purges and breathes, and the pair establish firm contact, typically gripping each other's right forearms. From there they make a slow, controlled ascent together, watching gauges and each other, adding a safety stop if gas allows.

The skill works when it is fast and undramatic, which is a training and configuration problem as much as a technique. The alternate must be clipped visibly in the triangle between chin and rib corners, not dragging in the sand, and both divers should know where it is before the dive, exactly what the buddy check confirms. Technical divers refine the pattern further: with a long hose configuration, the donor gives the primary regulator from their own mouth and switches to a necklaced backup, a sequence rehearsed as the S-drill before every dive.

Real air-sharing events almost always trace back to gas management failures, so the deeper lesson is prevention: plan turn pressures, check the SPG often, agree on signals during the buddy check, and surface with a real reserve. If you ever share air for real, in either role, write it up honestly in your dive log, the details are worth learning from.